Hello World Enterprise Edition

HelloWorld.java

import java.io.FileDescriptor;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintStream;

/**
 * Main class for the HelloWorld application.
 */
public class HelloWorld {
    private static HelloWorld instance;

    /**
     * Entry point of the application.
     * @param args Command line arguments.
     */
    public static void main(String[] args) {
        instantiateHelloWorldMainClassAndRun();
    }

    /**
     * Instantiate the main class and run its constructor.
     */
    public static void instantiateHelloWorldMainClassAndRun() {
        instance = new HelloWorld();
    }

    /**
     * Constructor for HelloWorld class.
     * Initializes and prints the HelloWorld string.
     */
    public HelloWorld() {
        HelloWorldFactory factory = HelloWorldFactory.getInstance();
        IHelloWorld helloWorld = factory.createHelloWorld();
        IHelloWorldString helloWorldString = helloWorld.getHelloWorld();
        IPrintStrategy printStrategy = helloWorld.getPrintStrategy();
        IStatusCode code = helloWorld.print(printStrategy, helloWorldString);
        if (code.getStatusCode() != 0) {
            throw new RuntimeException("Failed to print: " + code.getStatusCode());
        }
    }
}

/**
 * Factory class for creating HelloWorldString objects.
 */
class StringFactory {
    private static StringFactory instance = new StringFactory();

    /**
     * Get the singleton instance of StringFactory.
     * @return The singleton instance.
     */
    public static StringFactory getInstance() {
        return instance;
    }

    /**
     * Create a HelloWorldString object.
     * @param str The string to be wrapped.
     * @return A HelloWorldString object.
     */
    public HelloWorldString createHelloWorldString(String str) {
        HelloWorldString s = new HelloWorldString();
        s.s = str;
        return s;
    }
}

/**
 * Factory class for creating IPrintStrategy objects.
 */
class PrintStrategyFactory {
    private static PrintStrategyFactory instance = new PrintStrategyFactory();

    /**
     * Get the singleton instance of PrintStrategyFactory.
     * @return The singleton instance.
     */
    public static PrintStrategyFactory getInstance() {
        return instance;
    }

    /**
     * Create an IPrintStrategy object.
     * @return An IPrintStrategy object.
     */
    public IPrintStrategy createIPrintStrategy() {
        IPrintStrategy printStrategy = new PrintStrategyImplementation();
        IStatusCode code = printStrategy.setupPrinting();
        if (code.getStatusCode() != 0) {
            throw new RuntimeException("Failed to create IPrintStrategy: " + code.getStatusCode());
        }
        return printStrategy;
    }
}

/**
 * Implementation of the IPrintStrategy interface.
 */
class PrintStrategyImplementation implements IPrintStrategy {
    private OutputStream print;

    /**
     * Setup the output stream for printing.
     * @return Status code of the setup operation.
     */
    public IStatusCode setupPrinting() {
        try {
            FileDescriptor descriptor = FileDescriptor.out;
            print = new FileOutputStream(descriptor);
            return new StatusCodeImplementation(0);
        } catch (Exception e) {
            return new StatusCodeImplementation(-1);
        }
    }

    /**
     * Print the HelloWorld string to the output stream.
     * @param string The HelloWorld string to be printed.
     * @return Status code of the print operation.
     */
    public IStatusCode print(IHelloWorldString string) {
        try {
            print.write(string.getHelloWorldString().getHelloWorldString().concat("\n").getBytes("UTF-8"));
            return new StatusCodeImplementation(0);
        } catch (Exception e) {
            return new StatusCodeImplementation(-1);
        }
    }
}

/**
 * Implementation of the IStatusCode interface.
 */
class StatusCodeImplementation implements IStatusCode {
    private int code;

    /**
     * Constructor to set the status code.
     * @param code The status code.
     */
    public StatusCodeImplementation(int code) {
        this.code = code;
    }

    /**
     * Return the status code.
     * @return The status code.
     */
    public int getStatusCode() {
        return code;
    }
}

/**
 * Class representing a HelloWorld string.
 */
class HelloWorldString {
    String s;

    /**
     * Return the HelloWorld string.
     * @return The HelloWorld string.
     */
    public String getHelloWorldString() {
        return s;
    }
}

/**
 * Implementation of the IHelloWorldString interface.
 */
class HelloWorldStringImplementation implements IHelloWorldString {
    /**
     * Factory pattern to create HelloWorldString instance.
     * @return A HelloWorldString object.
     */
    public HelloWorldString getHelloWorldString() {
        StringFactory factory = StringFactory.getInstance();
        HelloWorldString s = factory.createHelloWorldString("Hello, World!");
        return s;
    }
}

/**
 * Factory class for creating IHelloWorld objects.
 */
class HelloWorldFactory {
    private static HelloWorldFactory instance = new HelloWorldFactory();

    /**
     * Get the singleton instance of HelloWorldFactory.
     * @return The singleton instance.
     */
    public static HelloWorldFactory getInstance() {
        return instance;
    }

    /**
     * Create an IHelloWorld object.
     * @return An IHelloWorld object.
     */
    public IHelloWorld createHelloWorld() {
        IHelloWorld helloWorld = new HelloWorldImplementation();
        return helloWorld;
    }
}

/**
 * Implementation of the IHelloWorld interface.
 */
class HelloWorldImplementation implements IHelloWorld {
    /**
     * Return the HelloWorld string implementation.
     * @return An IHelloWorldString object.
     */
    public IHelloWorldString getHelloWorld() {
        IHelloWorldString string = new HelloWorldStringImplementation();
        return string;
    }

    /**
     * Return the print strategy implementation.
     * @return An IPrintStrategy object.
     */
    public IPrintStrategy getPrintStrategy() {
        PrintStrategyFactory factory = PrintStrategyFactory.getInstance();
        return factory.createIPrintStrategy();
    }

    /**
     * Print the HelloWorld string using the provided strategy.
     * @param strategy The print strategy to use.
     * @param toPrint The HelloWorld string to print.
     * @return Status code of the print operation.
     */
    public IStatusCode print(IPrintStrategy strategy, IHelloWorldString toPrint) {
        IStatusCode code = strategy.print(toPrint);
        return code;
    }
}

/**
 * Interface representing a HelloWorld string.
 */
interface IHelloWorldString {
    /**
     * Return the HelloWorld string.
     * @return A HelloWorldString object.
     */
    public HelloWorldString getHelloWorldString();
}

/**
 * Interface representing a HelloWorld object.
 */
interface IHelloWorld {
    /**
     * Return the HelloWorld string implementation.
     * @return An IHelloWorldString object.
     */
    public IHelloWorldString getHelloWorld();

    /**
     * Return the print strategy implementation.
     * @return An IPrintStrategy object.
     */
    public IPrintStrategy getPrintStrategy();

    /**
     * Print the HelloWorld string using the provided strategy.
     * @param strategy The print strategy to use.
     * @param toPrint The HelloWorld string to print.
     * @return Status code of the print operation.
     */
    public IStatusCode print(IPrintStrategy strategy, IHelloWorldString toPrint);
}

/**
 * Interface representing a status code.
 */
interface IStatusCode {
    /**
     * Return the status code.
     * @return The status code.
     */
    public int getStatusCode();
}

/**
 * Interface representing a print strategy.
 */
interface IPrintStrategy {
    /**
     * Setup the output stream for printing.
     * @return Status code of the setup operation.
     */
    public IStatusCode setupPrinting();

    /**
     * Print the HelloWorld string to the output stream.
     * @param string The HelloWorld string to be printed.
     * @return Status code of the print operation.
     */
    public IStatusCode print(IHelloWorldString string);
}